1. Field of the Invention
The present invention relates to a mobile radio communications method and a mobile subscriber terminal for use in a system where a home mobile switch and visitor mobile switch are interconnected by a telecommunications network to allow a mobile terminal to communicate with other terminals, no matter where it roams in their service areas. More particularly, the present invention relates to a mobile radio communications method which supports global roaming services to enable one subscriber to call another subscriber who is visiting abroad, and also to a mobile terminal designed for such services.
2. Description of the Related Art
The advancement of radio telecommunications technologies has enabled us to enjoy mobile phone services in wide areas. With the international standards for mobile communications, we can use the same terminal equipment in both domestic and overseas areas through the facilities known as global roaming services. The code-division multiple access (CDMA) systems, for example, are deployed in the United States, Canada, Korea, China (Hong Kong), and other areas, allowing the users to roam from one country to another.
Suppose here that one mobile user in his/her home country is attempting to reach another mobile user who subscribes to global roaming services. When the called user happens to be roaming abroad, the calling user will eventually place an international call to the overseas destination. International phone calls, however, are much more expensive than domestic calls. The problem is that the calling mobile user is unable to know that he/she is calling (or has called) abroad, until the called person answers the call and the calling user receives a bill for it, because conventional mobile communications systems simply connect him/her to the specified destination terminal, regardless of whether it is in a domestic location or overseas location. After all, the calling user has to pay for an expensive international call that he/she made unintentionally.
In the case of domestic mobile phone services, most carriers provide a service of notifying a calling user of the duration and approximate cost of a phone call that he/she has just finished. Such existing notification services, however, do not address the problem described above because unintentional overseas connections cannot be avoided by merely sending a service usage report afterwards.